// 定义变量
$basic-color: yellowgreen;
$basic-width: 210px;

#app {
  border: 5px solid skyblue;
  .container {
    width: $basic-width;
    height: 150px;
    background-color: $basic-color;
    a {
      color: tomato;
      &:hover {
        color: yellow;
      }
    }
  }
}